The patient's T cells were found to secrete elevated amounts of interleukin-2 but failed to secrete two important B-cell stimulating factors, B-cell growth factor and B-cell differentiation factor, in response to PHA.

B cells from almost all of the CVID patients studied were unable to secrete any IgA in vitro, with or without IL-2, although all B cells tested from normal donors showed some spontaneous IgA secretion.